Foldable escape ladders are well known. When used as fire-escape ladders they are attached to the wall of a building adjacent at least one window. When not in use it is folded, in such a manner that an intruder could not use the ladder. In this folded state it is hardly noticeable. By activating a release mechanism it is possible to bring the ladder into its unfolded state. It then presents a ladder having its rungs horizontally and substantially transversely outwardly directed from the wall.
Many existing buildings do not today have sufficient fire- escape facilities. Many larger buildings for instance have one or more fire exits on each floor leading to some kind o f stairway. Very often, however, fire causes panic-resulting in a jam at the fire exits. This is a reason why people are killed by fire.
Another major problem exists with houses having only one or two floors, since that kind of houses rarely are equipped with fire exits. The reason being high costs for conventional fire escape arrangements. This is another reason why many people die of fire.
The above-identified problem could possibly be solved by using the basic type of ladders previously described, since such a ladder in principal could be cheaply and aesthetically mounted to a building.
So far many have tried to present such a ladder but still not with the success that ought to be possible. The reason for this, probably being that known ladders all present some kind of functional deficiencies. From EP-A-0 230 502, for instance there is known such a foldable fire escape ladder, made of metal, comprising at least two parallelly arranged strings, one inner string and one outer string, which are interconnected by means of a plurality of parallel rungs of which the ends are pivotally connected to the respective strings; said inner string being substantially channel shaped having an intermediate portion co-joining two portions extending substantially parallelly and comprising means for interaction with mounting means; said outer string being channel shaped having an intermediate portion co-joining two portions extending substantially parallelly; each of said rung having a hollow cross-section being substantially rectangular and further having pivoting points, abutting end portions and chamfered end portions; wherein in the folded state at least the major part of the rungs are received within a space delimited by said strings and wherein in the unfolded state each said abutting end portion interact with the inner surface of intermediate portion of each respective string in such manner that the rungs are kept substantially perpendicularly in relation to the strings.
The above-identified known ladder has shown to have certain deficiencies, especially concerning strength. In order to meet certain requirements of firmness, this ladder presents rungs being relatively short, about 40 cm. The intention being to limit the maximum moment acting on the abutments and on the pivot-points. Furthermore, it has shown that the ladder after a long time of use, probably due to extreme pressure at the abutting ends of the rungs, can cause an exceeding play so that the stability of the unfolded ladder decreases.